Properties, control and ICR-heating of the plasma in TEXTOR

Wolf, G.H.; Bay, H.L.; Bertschinger, G.; Bieger, W.; Bogen, P.; Brüssau, W. D.; Campbell, G. A.; Cao, Yang; Conn, R.W.; Dippel, K.H.; Esser, H. G.; Finken, K. H.; Fuchs, Gerhard; Giesen, B.; Goebel, Dan M.; Graffmann, E.; Hartwig, H.; Hintz, E.; Hoenen, F.; Höthker, K.; Kaleck, A.; Kever, H.; Könen, L.; Korten, M.; Li, L; Lie, H T; Leung, W.K.; Pontau, A.E.; Pospieszczyk, A.; Reiter, D.; Rogister, A.; Ross, G.G.; Rusbüldt, D.; Samm, U.; Schweer, B.; Schlüter, Jochen; Soltwisch, H.; Stodiek, W.; Thomas, George J.; Waelbroeck, F.; Waidmann, G.; Wienhold, P.; Winter, J.; Yamauchi, R.; Delvigne, T.; Descamps, P.; Durodié, F.; Jadoul, Michel; Koch, R.; Lebeau, D.; Messiaen, A.; Pearson, David; Vandenplas, P. E.; Nieuwenhove, R. Van; Oost, G. Van; Wassenhove, G. Van; Weynants, R.R.

doi:10.1088/0741-3335/28/9a/018

Cited by 26 publications

(8 citation statements)

References 12 publications

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“…First, in the reconnection model the central current profile is repeatedly flattened such that the safety factor q remains close to 1 over the central region; on the other hand, no such flattening occurs in the turbulent model, which therefore allows for a stronger peaking of the current profile and lower values of the on-axis safety factor q 0 . Recent observations of the current profile on TEXTOR show that q 0 can be well below 1 when sawteeth are observed [20]. This clearly supports the validity of the turbulent model.…”

Section: Summary and Discussionsupporting

confidence: 70%

Sawteeth, transport and electron cyclotron heating in T-10

Goedheer

Westerhof

1988

Nucl. Fusion

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The paper presents transport code simulations of sawteething discharges in T-10. Two models were employed to describe the sawtooth oscillations. In the first (reconnection) model the sawtooth collapse is caused by complete reconnection. In the second (turbulent) model the collapse is ascribed to increased radial transport caused by the generation of turbulence at some critical size of the m = 1, n = 1 magnetic island. For one particular discharge the predictions of the two models for the temperature, density and current profiles as well as the evolution of the heat pulse generated by the sawtooth collapse were analysed in detail and compared with the experiment. Also the influence of both central and off-axis heating by electron cyclotron waves on the sawtooth dynamics as given by the two models was investigated and compared with the experiment. In all respects good agreement with the experiment was obtained with the turbulent model. In contrast, it was not possible to obtain satisfactory simulations with the reconnection model. The failure of the reconnection model is mainly due to the general properties of the reconnection process and, consequently, is not characteristic of the specific model employed but applies to all models ascribing the sawtooth collapse to reconnection.

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Section: Summary and Discussionsupporting

confidence: 70%

Sawteeth, transport and electron cyclotron heating in T-10

Goedheer

Westerhof

1988

Nucl. Fusion

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“…(c) The calculated and measured (see Ref. [35]) values of the confinement time are compared in Fig. 8a, which shows that the code reproduces extremely well the observed degradation of the energy confinement time with additional power.…”

Section: Power Scanmentioning

confidence: 57%

“…(c) Figure 4 shows a comparison of the measured confinement times (diamagnetic measurements taken from Ref. [35], Fig. 10) with the calculated values.…”

Section: Density Scanmentioning

confidence: 99%

“…(a) These experiments were made on a different day. We have therefore derived a new value of Z eff (=1.27), using the numerical procedure described in Section 2.2.1 (a) and the plasma parameters measured [35] during the Ohmic shot of the series. The agreement with the values obtained in the density scan shows that the contamination level was the same for both scans.…”

Section: Power Scanmentioning

confidence: 99%

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Transport through dissipative trapped electron mode and toroidal ion temperature gradient mode in TEXTOR

et al. 1988

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A self-consistent transport code is used to evaluate how plasma confinement in tokamaks is influenced by the microturbulent fields excited by the dissipative trapped electron (DTE) instability. As shown previously, the saturation theory on which the code is based has been developed from first principles. The numerical results reproduce well the Neo-Alcator scaling law observed experimentally (for example in TEXTOR) in non-detached Ohmic discharges, the confinement degradation resulting when auxiliary heating is applied and a large number of other experimental observations. The potential impact of the toroidal ion temperature gradient (fy) mode on energy confinement is assessed by estimating the ion thermal flux with the help of the mixing length approximation. The temperature and density profiles measured in TEXTOR (q a = 2.45) are compared at either variable mean density or variable additional power, and their stability against DTE and 7j ; modes is checked; in the latter case, a new criterion is used, which is valid for arbitrary curvature. All profiles examined are marginally unstable for the two modes, essentially between the q = l and q=2 magnetic surfaces. The code results and the stability analysis lead to the following conclusions and suggestions: (1) The DTE instability is sufficient to explain the anomalous heat transport in low density discharges (attached plasmas) with or without additional heating; the marginal instability for the DTE mode thus follows from heat flux constraints. (2) The observed marginal instability against the JJ ; mode must then follow from particle flux constraints. (3) The condition that both y m and y DTE (y = growth rate) must be small is the restriction which determines the profiles that correspond to the experimental conditions and which determines, to a large extent, profile consistency. (4) Finally, it is suggested that the deviation from Neo-Alcator scaling, the density limit and the phenomenon of plasma detachment are interrelated effects which arise at high densities, when the constraint on the electron heat flux becomes harder to satisfy.

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“…Plasma heating by electromagnetic waves was largely improved, 21 and the accessible density regime had been increased by a factor of ;1.5. An initial reduction of oxygen by a factor of ;5 compared to metallic surfaces has been observed.…”

Section: Iiia Carbonizationmentioning

confidence: 99%

Wall Conditioning on TEXTOR

Philipps

2005

Fusion Science and Technology

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Properties, control and ICR-heating of the plasma in TEXTOR

Cited by 26 publications

References 12 publications

Sawteeth, transport and electron cyclotron heating in T-10

Sawteeth, transport and electron cyclotron heating in T-10

Transport through dissipative trapped electron mode and toroidal ion temperature gradient mode in TEXTOR

Wall Conditioning on TEXTOR

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